A Fan in Sudan
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This spot is located in the southeastern end of Sudan, and is a fan facing the Red Sea. The southern portion of this image falls on the foot of Mt.Hamoyet, which is 2,780m high. In the west, can be seen a green line, which is a wadi, called ths Baraka River. A wadi is a river whose riverbed is normally dry except when it rains.
Around the upper reached of the Baraka River are a number of wadis of various sizes. Only dry sand and earth usually exist on the riverbed, but when it rains a few times a year in the desert, it pours like an avalanche. This rain water flows to the Baraka River, turning it into a rapid stream and spilling onto the plains. The waterflow containing an enormous amount of sand and earth grows into innnumerable tributary waters, carrying and accumulating sand and earth from the foot of the mountain to the sea which subsewuently forms a delta plain over a long time. This kind of plain is specific to the one formed at the foot of the mountains in a dry region. It shows that the Baraka River is a whitish dry land around the plain, while it turns into a green land near the coast. This is a special phenomenon for fans where a river flows underground and its riverbed is piled with permeatable rubble, but streams come to the surface when they reach a plain, watering the earth.
Further ahead, it forms a delta where fine sands and earth flow out to the sea.
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